PROJECT SUMMARY/ABSTRACT The overall goal of this R03 proposal is to support Dr. James Andrews? in becoming an independent physician-scientist focused on Alzheimer?s disease (AD) and Alzheimer?s disease related dementias (ADRD) research and the prevention of physical disability among older adults with Alzheimer?s disease. The proposed project builds upon Dr. Andrews? expertise in sarcopenia and hospital-associated disability among older adults and will leverage his existing research infrastructure to conduct novel studies on the role of sarcopenia in the development of hospital-associated activity of daily living (ADL) disability among older adults with Alzheimer?s disease and Alzheimer?s disease related dementias. Coupled with a rigorous professional development plan focused on gaining specific training around assessment of functional status in older adults with Alzheimer?s disease and ADRD as well as advanced skills in epidemiology and biostatistics, the proposed project leverages the University of Washington?s world-class investigators, facilities, and mentorship opportunities to allow Dr. Andrews to achieve his goal of being an independent clinical investigator in aging and dementia. This project?s primary research objective is to test the central hypothesis that baseline sarcopenia (low lean mass and strength) and changes in sarcopenia while hospitalized, are both associated with risk of new ADL disability in older adults with Alzheimer?s disease and ADRD. Inability to perform ADLs is a primary cause of reduced quality of life and health care utilization in AD. Hospitalization is strongly associated with development of ADL disability in older adults, especially in those with AD. In addition, during hospitalization an older adult?s muscle mass and strength decline. However, the relationship of sarcopenia with the risk of hospital-associated ADL disability among older adults with AD and ADRD is not known. An improved understanding of this relationship is urgently needed to develop novel interventions that prevent hospital-associated ADL disability and improve quality of life for the millions of Americans living with dementia. Aim 1 leverages the Health ABC Study, a population-based longitudinal cohort of adults aged ? 70 years to advance understanding of the long-term relationships between sarcopenia and hospital-associated ADL disability in older adults with Alzheimer?s and related dementias. Aims 2 leverages existing research infrastructure to conduct a pilot prospective cohort study of hospitalized adults aged ? 70 years with and without Alzheimer?s and related dementias examining sarcopenia at admission and changes in sarcopenia during hospitalization as risk factors for hospital-associated ADL disability. The proposed aims will be among the first to examine aging-related sarcopenia as a risk factor for hospital-associated ADL disability in older adults with AD and ADRD. Findings from this project will directly inform future R01 proposals to conduct large prospective cohort studies of hospitalized older adults with Alzheimer?s disease and related dementias focused on changes in sarcopenia during hospitalization as important predictors of long-term functional outcomes of hospitalization in these patients.